Monday, June 20, 2011

The Soto OD-1R Microregulator: Cold weather problems solved?

Rich wrote:
Just got the Soto OD-1R microregulator stove... I read the regulator solves the cold weather problems... 
Well, Rich, I've got good news, and I've got bad news.

The good news is that a regulator might help in colder weather, perhaps to the tune of about five degrees Fahrenheit. In other words, if a "normal" (needle valved) burner would conk out at 25F, you might still be able to operate a regulator valved burner down to 20F. But that's it: about five degrees F difference. And other factors could affect that five degree difference.  Note the use of the word "might."  Look for more on that in future blog posts.

The real issue is the type of fuel. Each of the common types of fuel used for backpacking stoves has a vaporization point. Below that vaporization point, the fuel will remain a liquid, and
an upright canister stove (such as the OD-1R), no matter how cleverly built, will simply not function. The three common fuels and their vaporization points are:
"Plain" butane: +31F (-0.5C)
Isobutane: +11F (-12C)
Propane: -44F (-42C)

If you consider the entire "lifespan" (full to empty) of a canister, an upright canister stove can only function at a temperature about ten Fahrenheit degrees above the highest vaporization point of all fuel components.  For example, if you have a fuel mix of propane and isobutane, the highest vaporization point is +11F, and you can only operate an upright canister stove down to about +20F (roughly ten degrees above the vaporization point of isobutane, the fuel component with the highest vaporization point).

Therefore, the first trick of operation for gas stoves in cold weather is to choose good fuel. Avoid "plain" butane. For example, Primus, Optimus, Glowmaster, and Coleman brand gas canisters contain at least some "plain" butane. Avoid these and similar brands for cold weather use. Instead get brands that contain only isobutane and propane (Snowpeak, MSR, etc.). These brands will work down to about 20F (at sea level)*. Note that as you use the gas on an upright canister stove, the temperature of the fuel will fall, so even if you start with fuel at 20F, by the time you finish cooking, the fuel may have become much colder, and your flame may weaken or die. Indeed, even on days where the outside temperature is above 32F, the temperature of the fuel may dip below freezing, like this:

The more fuel you burn, the colder the fuel will become.

Which leads us to: The second trick of operation for gas stoves in cold weather is the temperature of the fuel. If you can keep the fuel warm, the gas will flow even in weather where a stove wouldn't normally be able to operate. Check out my Stoves for Cold Weather I article in Seattle Backpacker's magazine for tips on how to keep the fuel warm. 

If you're really interested in a gas stove for cold weather, you need to look at a different class of stoves, the class generally referred to as remote inverted canister stoves.  I've written article on remote inverted canister gas stoves for cold weather:  Stoves for Cold Weather IIA couple of examples of remote inverted canister, cold weather capable gas stoves include:
-The Coleman Xtreme (The "gold standard" of cold weather gas stoves).
-The MSR Rapidfire (An economical cold weather gas stove).

 An upright canister stove like the Soto just isn't going to cut it in real cold weather, regulated burner not withstanding.. 

So, in summary, your first concern when running a gas stove in cold weather is the fuel itself.  The second is the temperature of the fuel.  Third, if you need to go really cold, you need to switch to a different class of stoves -- remote inverted canister stoves.  The design of the valve on the burner is of little consequence in comparison to the the fuel, the temperature of the fuel, and the class of stove.


*When I say 20F, I mean throughout the life of the canister, particularly towards the end of the canister. Fresh (full) canisters will work in colder temperatures. For gas stoves, it is always the temperature of the fuel that matters, not the air temperature.

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